The present invention relates to radio communications, and more particularly, to provision of data links over radio channels.
A relatively fertile area of innovation in wireless communications is the development of applications that utilize radio protocols for unlicensed, ad hoc short range radio communications, such as those specified under the IEEE 802.11 and Bluetooth™ specifications. For example, laptop computers, printers, personal digital assistants (PDAs), cellular handsets, headsets and the like are increasingly being offered with interfaces that allow such devices to create short range radio connections amongst themselves or with network nodes, such as network access points.
Telephony profiles for Bluetooth™ devices have been developed. The Cordless Telephony Profile (CTP) specified by the Bluetooth™ Special Interest Group (SIG), available on the Web at bluetooth.org, utilizes a Bluetooth™ synchronous connection-oriented (SCO) channel to transmit voice data from a vocoder circuit at a fixed rate of 64 kilobits/second. The format of the voice data is either A-law or μ-law pulse code modulation (PCM) or continuous variable-slope delta (CVSD) modulation. The CTP specification also allows for a transparent format whereby some arbitrary coding may be used to generate the 64 kb/s data stream, as the SCO specification does not allow for retransmission. Ericsson's Mobile Services Profile (MSP) uses a Bluetooth™ asynchronous connection-less (ACL) channel with retransmission capability to transmit voice data from a vocoder circuit at a fixed rate of approximately 12.2 kb/s.